| 内蒙古海勒斯台俯冲增生混杂岩地质特征及发现的意义 |
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| 引用本文： | 林敏,马昌前,徐立明,李玉娟,杨仲,汤建荣.内蒙古海勒斯台俯冲增生混杂岩地质特征及发现的意义[J].地球科学,2019,44(10):3279-3296. |
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| 作者姓名： | 林敏 马昌前 徐立明 李玉娟 杨仲 汤建荣 |
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| 作者单位： | 1.中国地质大学资源学院, 湖北武汉 430074 |
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| 基金项目： | 中国地质调查局地质调查项目DD20190039 |
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| 摘 要： | 采用"造山带混杂岩区"新理论，首次在贺根山-黑河缝合带中段发现海勒斯台俯冲增生混杂岩，建立由"基质"+"岩块"组成的俯冲增生杂岩体系，其构造样式为整体左行逆冲剪切.基质主要有糜棱岩、千糜岩、超糜棱岩及少量的沉凝灰岩、粉砂岩、细砂岩，构造环境为弧前盆地，时代主要为中寒武世；岩块有洋岛海山岩块、弧后洋盆洋壳残片、火山弧岩块、裂离陆块，岩块的年龄区间主要在中寒武世-中奥陶世，裂离陆块时代为新太古代.结合俯冲增生杂岩基质年龄、岩块的年龄、侵入混杂岩的TTG年龄（449 Ma）和变形程度、接触关系等，将海勒斯台俯冲增生杂岩的形成时代厘定为中晚奥陶世.认为研究区俯冲作用在早寒武世就已经开始，在大陆边缘形成火山岛弧；奥陶纪初期弧后发育弧后盆地，至中奥陶世弧后盆地出现洋壳；此时中寒武世的基质经俯冲下切后在中奥陶世时期折返上升；晚奥陶世时期由于区域的持续汇聚挤压，该弧后洋盆很快夭折；弧陆开始碰撞，导致双向俯冲.在弧陆碰撞过程中，晚期形成的弧后盆地洋壳等新岩块混入早期形成的基质中.海勒斯台俯冲增生混杂岩带的发现填补了贺根山-黑河缝合岩带中段的空白，对区域构造格架厘定具有非常重要的意义，为研究古亚洲构造域演化提供了新的证据.
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| 关 键 词： | 内蒙古 海勒斯台 构造混杂岩 俯冲增生 早古生代 岩石学 |
| 收稿时间： | 2019-08-08 |
Geological Characteristics of Subduction-Accretionary Complexes in Hellestein District,Inner Mongolia and Its Discovery Significance |
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| Abstract: | The Hellestein subduction accretive mélange occurs in the middle part of the Hegen Mountain-Heihe suture zone, and its structural style is left thrust shear as a whole. The accretive mélange consists of matrix and rock complex. The main matrix is composed of mylonite, phyllonite, ultramylonite and a small amount of tuff, siltstone and fine sandstone. The tectonic environment is a pre-arc basin and the age is mainly Middle Cambrian. The rock complex includes oceanic island seamount rock block, back-arc oceanic basin oceanic crust fragment, volcanic arc block and rift continental block. The age of the complexes ranges mainly from Middle Cambrian to Middle Ordovician. Based on the deformation degree and contact relationship of subduction accretion complex, and combined with the age of matrix, rock complex and TTG rock series, the age of formation of Hellestein subduction accretion complex is determined as Middle-Late Ordovician. The subduction of this area began in the Early Cambrian and formed a volcanic island arc on the continental margin, then the back-arc basin developed in the Early Ordovician, and the oceanic crust appeared in the back-arc basin of the Middle Ordovician. At the same time, the Middle Cambrian matrix returned to rise in the Middle Ordovician after subduction. In the end, the back-arc oceanic basin soon died due to the continuous regional convergence and compression of plate in the Late Ordovician. The arc land began to collide, leading to bidirectional subduction. During the process of arc-continent collision, the new blocks of the back-arc basin formed in the late stage were mixed into the matrix formed in the early stage. |
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